Phone numbers
Phone numbers are a funny thing.
Once we wanted to have our country code added to all customers phone numbers for SMS messages.
Of course this was outsourced to some foreign company, so when the developer got the translated instructions equivalent to add +44 to all phone numbers, the foreign developer just disabled his brain and did a mathematically +44 to all our phone numbers.Like it would make some sort sense.
After getting lots of complaints the week later, it was rolled back, and the developer was told what it means to add the country code to a phone number.
Translation errors, or lack of cultural understanding can result in lots of issues.